Safety Analysis Of Highway Tunnel Structure With Cracked Secondary Lining And Crack Control Countermeasures

In recent decades,the country 's infrastructure has been vigorously developed,and China 's road network has been basically improved.The follow-up will gradually shift from a large-scale construction period to a combination of construction,maintenance and reinforcement.With the growth of highway operation years,more and more highway tunnels are exposed to external forces,the lining material is deteriorated,and the holes behind the lining cause the tunnel diseases to become increasingly prominent.The most common disease is the cracking of the secondary lining of the tunnel.The cracking of the secondary lining of the tunnel affects the bearing capacity and stability of the structure to a certain extent,which makes the concrete fall off and drop blocks,and even arch fall seriously,thus affecting the normal operation of pedestrians and vehicles.In order to ensure the safe and normal operation of the tunnel,it is necessary to detect and monitor the cracks in the lining of the tunnel,and evaluate the impact of cracked lining on the safety of the structure,so as to provide technical basis for the maintenance and reinforcement of the tunnel.Based on the long-term monitoring project of secondary lining cracks in a highway tunnel,this paper systematically summarizes the classification of lining cracks and analyzes the preliminary causes of lining cracks;In view of the shortcomings of the current standard method on the evaluation method of tunnel cracks,a comprehensive evaluation method combining qualitative and quantitative methods is proposed and the evaluation standard is made.Using crack length,width,depth and crack deformation rate as evaluation indexes,80 cracks in the tunnel lining were evaluated and graded and then using the finite element software MIDAS/GTS to carry out the safety calculation of the typical lining section.The calculation results show that the bearing capacity of the lining at this location is reduced due to the existence of cracks,which leads to the redistribution of the force distribution law of the entire lining structure.The axial force,shear force and bending moment of the vault and side wall are no cracks The situation has increased a lot.According to the Griffith criterion,the bearing capacity checking calculation is carried out,and the lining at the arch and invert of the lining section is determined to be the most dangerous and prone to cracking.Due to the existence of cracks,the concrete is damaged and the bearing capacity is reduced.The closer to the crack,the more likely it is to crack.The existence of cracks reduces the safety factor of the lining structure.Among them,the safety factor of the structure at the vault has dropped the most,and has not met the requirements of the code.It is urgently needed to be strengthened.Finally,based on the crack assessment level and the safety analysis results,comprehensive methods such as direct smearing method,chiseling and embedding method,carbon fiber reinforcement,anchor grouting and bushing reinforcement are adopted to formulate the tunnel crack repair and reinforcement method in a targeted manner.